Preparatory work for the update of the tolerable upper intake levels for vitamin B6

Abstract

To support EFSA in the preparatory work for the assessment of Tolerable Upper Intake Levels (UL) for vitamin B6, a tailored ‘high level’ protocol was developed, based on a template protocol and taking into account the specificities of vitamin B6. This protocol outlined the methods, the relevant endpoints and priority adverse health effects in relation to high intakes of vitamin B6. Systematic reviews (SR) were conducted following a tailored literature search, data extraction, evidence appraisal (i.e. risk of bias (RoB) assessment) and evidence synthesis. Narrative reviews (NR) were conducted to gather contextual evidence relevant to the interpretation of the main body of evidence. In the SR on the dose-response relationship between vitamin B6 and peripheral neuropathy, 3793 records were identified and reduced to 32 individual records after screening for eligibility. The evidence appraisal revealed an overall moderate to high RoB of the individual studies and an overall rating of the total body of evidence as very low due mainly due to the type of data from case studies/case reports and limited number of other data. The available evidence confirmed a high degree of inter-individual variability to sensitivity to a high exposure of vitamin B6 in relation to development of peripheral neuropathic outcomes but did not allow to determine a No Observed Adverse Effect Level or Lowest Observed Adverse Effect Level. In the SR on developmental toxicity, 4941 records were identified and reduced to 23 individual records including human and animal studies after screening for eligibility. The available data demonstrated a high degree of heterogeneity with respect to exposure and adverse health outcomes and overall, showed no positive or causal relationship between vitamin B6 intake and adverse developmental effects, including congenital defects. The NRs showed a paucity of data on high intake of vitamin B6 vitamers and their metabolism.